Use of Biogenic Immunomodulators to Enhance Early Intestinal Development and Mucosal Immunity to Enteric Pathogens in Broiler Chickens

NON-TECHNICAL SUMMARY: Broiler chickens are regarded as Alabama\'s #1 agricultural commodity because they contribute the highest (about 41%) amount of total farm and forestry receipts in the state. Therefore, broiler chicken production is an economically important industry in the state of Alabama and in the USA as a whole. Sadly, the broiler industry is plagued by the fact that live broilers on the farms have been implicated as important vehicles for transmitting foodborne pathogens such as Salmonella spp. and campylobacter spp. to humans. This is because antimicrobials typically present in broiler feed are thought to interact with these intestinal bacteria in the bird in a manner that triggers the bacteria to mutate into drug-restistant strains. Thus, when live broilers habouring such resistant bacteria are slaughtered and processed for meat, if their intestine ruptures, the intestinal contents containing the resistant bacteria can contaminate the harvested meat. If the bacteria survives the chemical control processes in the chiller tank and the meat ends up in grocery stores, humans that buy and consume such contaminated meat often fall sick with foodborne gastroenteritis if the meat is improperly cooked. More important is the fact that such gastroenteritis is difficult to treat due to the drug-resistant nature of the causative bacteria. In fact, mortality sometimes results. Thus, there is increasing consumer and governmental pressure on the broiler industry to ban the inclusion of drugs in poultry feed. This has prompted poultry scientists to look for natural, safer alternatives for controlling intestinal pathogens in poultry. Application of biogenic (natural) immunomodulators to the feed or water of chickens is a natural potential method of achieving pathogen control without using drugs. Such immunomodulators (nucleotides, beta-glucans, probiotics, and prebiotics) are expected to enhance the development of the intestinal immune system (which is typically immature at the time the chick hatches), thereby improving resistance to intestinal pathogens. Intestinal pathogens of significant economic concern to the poultry industry include Salmonella spp., Campylobacter spp., Clostridium perfringens, and Eimeria spp. While Salmonella spp. and Campylobacter spp. are important foodborne pathogens, Clostridium perfringens and Eimeria spp. cause economic loss to the broiler industry in terms of their disease symptoms which include reduced weight gain, increased condemnations at market, and high mortality. Taken together, it is imperative to identify effective immunomodulators for pathogen control in the poultry industry. At the end of the proposed study, such immunomodulators will be identified and made known to poultry producers in Alabama through presentations. Inclusion of such effective immunomodulators into broiler diets or drinking water is expected to facilitate the elimination of antimicrobial drugs in broiler chicken diets and promote the availability of drug-free broiler meat for human consumption. In turn, this will probably increase the sales of poultry meat, and ultimately increase monetary returns to broiler producers in Alabama and USA. <P>
APPROACH: Day old chicks will be obtained from a commercial hatchery and randomly partitioned into experiment treatments derived by varying the levels of dietary antimicrobial (with or without), immunomodulator (with or without), and pathogen challenge (with ot without). Next, pens in Petersime Brooder Batteries will be randomly assigned to experimental treatments in a randomized complete block (RCBD) design such that each treatment utilizes 4 replicate pens. Experimental diets will consist of a basal (conventional) corn-soybean meal Starter (0-3 weeks) and Grower (3-6 weeks) diets formulated to meet or exceed National Research Council (NRC) recommendations (NRC, 1994). Immunomodulators will be administered in feed or drinking water at levels recommended by manufacturers or at appropriate levels determined from literature. Birds will be given ad libitum access to feed and water, and the environment in the room containing the Petersime Brooder batteries will be controlled to provide temperature and ventilation designed to optimize bird health and development. Birds will be observed twice a day and mortality will be recorded throughout the duration of experiment (28 or 49 days). During the experiment, chicks will be challenged with one of the following pathogens; Salmonella, Campylobacter, Coccidia (Eimeria spp.), and Clostridium perfringens. At 1, 3, 5, 12, and 18 days post-challenge, the following will be done; A) Collection of intestinal samples (from duodenum, jejunum, and ileum) followed by analysis of activities of brush border enzymes (sucrase-isomaltase (SIM) and alkaline phosphatase (ALP)) in order to assess intestinal maturation. SIM and ALP are widely accepted as markers of enterocyte differentiation and maturation (Uni et al., 2000; Jeurissen et al., 2002). Next, portions of these same tissues will be subjected to Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) and Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SDS-PAGE)analyses for the identification of genes and proteins whose expression was induced by pathogen challenge, respectively. B) Levels of challenge pathogen in the intestine will be microbiologically enumerated. C) Pathogen-specific antibody (IgA and IgG) titers will be determined in intestinal flushes and serum. D) Growth performance will also be evaluated weekly by calculating body with (BW), BW gain, and feed conversion. All data obtained will be subjected to GLM procedures of SAS. Difference between means will be detected with Duncan\'s multiple range test. Level of significance that will be accepted is p < 0.05. Lastly, results of all analyses will be collated and used to determine if the immunomodulator used was effective in enhancing intestinal immunity to the challenge pathogen.